Jagtar, a 31-year-old football fan from Dumbarton, was arrested by plain clothes officers while shopping with his new wife shortly after their wedding.

His family has been unable to see him since, his wife, who has not been named, is in hiding and on Friday he spent his birthday in a cell far from home with no release date in sight.

The case, backed by the #FreeJaggiNow hashtag on social media, has attracted support from the Sikh diaspora in Canada and America.

Yesterday Gurpreet revealed he and another family member had travelled to India to aid their brother and speak with British consular staff in the wake of his November 4 arrest but had to leave shortly after arriving for fear of their safety.

He said: "Our lives became at risk so we had to leave on November 9, not by choice.

Internet marketer Jagtar, known as Jaggi, has yet to be charged, but local media reports have linked his arrest to the killings of prominent Hindu figures, as well as that of a Christian. The action has also been attributed to his involvement with a website which publishes material on anti-Sikh violence in the 1980s.

Gurpreet claims police have "got the wrong person" and are holding his brother "to save face".

Jagtar has been considered vulnerable since he accused police in the Punjab region of torturing him and Gurpreet repeated his criticism of the Foreign and Commonwealth Office, who he says have failed to prioritise Jagtar's safety over "trade deals", stating: "That's all they are concerned about."

Meanwhile, the 90-day pre-charge period has elapsed and Jagtar, who has spent periods in isolation, has still been unable to meet with UK officials in private.

He said: "Various allegations have been made against Jaggi that he has been accused of funding right-wing murders, however no evidence has been provided in relation to any of this.

"No charge sheet has been filed and 100 days on we are still waiting to hear what exactly Jaggi has been charged with.

"We are also concerned that the UK Government are not able to protect its citizens. Jaggi has been subject to third degree torture, extreme action was promised but it's not been taken.

"On November 7 the chief minister of Punjab stated they had all the evidence but 100 days on it still isn't clear.”

The FCO says it is assisting the family, but West Dunbartonshire MP Martin Docherty-Hughes insisted it needs to "up its game", adding: "It’s now 100 days that my constituent has been held by the Indian authorities and he has yet to be charged with any crime.

“Jagtar’s family in Dumbarton are deeply concerned for his welfare. He is their son, their brother and their friend – and they remain determined to secure justice for Jagtar and bring him home to Scotland.

“It’s critical that the family receives the full backing of the UK government. I will continue doing all I can to support the family and ensure Jagtar is treated fairly and afforded an open and transparent judicial process.”

Appealing to the public to write to their MPs and MSPs to press for action, Gurpreet said: "We are calling on all our Scottish brothers and sisters and the wider UK family.

"This can only be achieved with your support."

On his message to Indian authorities, he went on: "If Jaggi has done anything, charge him. If he has not done anything, release him."

Josie Fathers of human rights organisation Redress said: "Jagtar's treatment to date raises concerns about the chances of him being subject to further torture and ill treatment.

"He remains without charge and has been virtually isolated from the outside world.

"In December, Redress urged UN special rapporteur on torture to intervene in Jagtar's case to ensure that he is protected from ill treatment.

"When there are strong allegations of torture the special rapporteur has the power to request the government of India that any alleged ill treatment is stopped and investigated.

"We continue to urge him to intervene and hope there is progress ahead of the Human Rights Council in March."

The FCO said: "Our staff continue to support a British man and his family following his detention in Punjab.

"We continue to press the Indian authorities for further access to ensure he can receive the necessary consular assistance."

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